This invention relates generally to pens for inkjet printers, and more specifically to determining the turn-on voltage for such pens.
Inkjet printers have become increasingly inexpensive and increasingly popular, especially for home computer users. A typical inkjet printer usually has a number of common components, regardless of its brand, speed, and so on. There is usually a print head that contains a number of pens, where each pen has a series of nozzles used to spray drops of ink onto paper. Alternatively, the pens may be separate, and not located on a common print head. Ink cartridges, either integrated into the print head or separate therefrom, supply the ink. There may be separate black and color cartridges, color and black in a single cartridge, a cartridge for each ink color, or a combination of different colored inks in a given cartridge.
A print head motor typically moves the print head assembly back and forth horizontally, or laterally, across the paper, where a belt or cable is used to attach the assembly to the motor. Other types of printer technologies use either a drum that spins the paper around, or mechanisms that move the paper rather than the print head. The result is the same, in that the print head is effectively swept across the paper linearly to deposit ink on the paper. Rollers pull paper from a tray, feeder, or the user""s manual input, and advance the paper to new vertical locations on the paper.
For the pens to fire their nozzles, resulting in ink sprayed on the paper inserted in the printer, a turn-on voltage is applied. The turn-on voltage causes the nozzles to fire. The turn-on voltage for each pen is desirably precisely known, so that only the exact turn-on voltage is applied to fire the nozzles of a pen. If a greater voltage is applied, the voltage in excess of the turn-on voltage is typically converted into heat. The ink may therefore increase in temperature beyond its recommended setting, which may cause printing quality to decrease. For example, too much ink may be deposited on the paper, or printing artifacts may otherwise be deposited on the paper. Furthermore, excess voltage may result in greater wear-and-tear on the pens and their nozzles, causing them to fail prematurely.
Although the inkjet printer pens in theory have a common specified turn-on voltage, in actuality the turn-on voltage for each pen varies depending on a number of different factors. Manufacturing tolerances may cause the turn-on voltages for different pens, as well as for different nozzles within the same pen, to vary. Other voltage errors may result from variations within the inkjet printer itself. For example, the traces and other electrical connections and components within the printer may have electrical resistances less than or greater than specified amounts, such that voltage drops across these connections and components may be less than or greater than what is expected. This means that the actual voltage applied to the inkjet printer pens to turn them on may vary from nozzle to nozzle, from pen to pen, and from printer to printer, effectively causing the turn-on voltages of the pens to vary.
These variations mean that using a common theoretical specified turn-on voltage for each pen in each printer will likely cause a decrease in printing quality and result in printing artifacts to develop on the media printed on by the printers. Even determining the turn-on voltages for the pens in isolation, without considering the specific printer in which they are being used, may cause such printing quality degradation. For these and other reasons, therefore, there is a need for the present invention.
The invention relates to determining the turn-on voltage for inkjet printer pens. An inkjet printer has a number of pens, and a number of sets of nozzles in each pen. Each set of nozzles of a pen is fired at each of a number of voltages, to obtain a voltage-value curve for each set of nozzles. A nozzle turn-on voltage for each set of nozzles is determined based on a maximum slope of its voltage-value curve. The turn-on voltage for each pen is determined based on the nozzle turn-on voltages of the voltage-value curves for its sets of nozzles.
Still other aspects, embodiments, and advantages of the invention will become apparent by reading the detailed description that follows, and by referring to the accompanying drawings.